STUCTURE AND FUNCTION OF ORGANELLE

  STUCTURE AND FUNCTION OF ORGANELLE 

                                             

                                                  NUCLEUS

    >Sphere or oval

    >Double membrane organelle 

    >Carry genetic information 

    >Direct protein synthesis 

    >Consist nuclear envelope,nuclelous and chromatin

Nuclear envelope:>Double membrane separate nuclear content 
                                            from surrounding cytoplasm

Nucleoplasm:>Interior part of nucleus with full of chromatin

Nuclelous:>A mass of densely stained granules and fibres
                   adjoining part of chromatin

                 >Spherical in shape 

                 >Non membranous

                 >Function:Produce rRNA,form ribosome 

ENDOPLASMIC RETICULUM

   >Network of membranous sacs and tubes 

   >Continues with nuclear envelope

     

Smooth ER:>Has lack of ribosome on its outer surface

                    >Synthesis of lipid

                    >Metabolism of carbohydrate 

                    >Detoxification of drugs and poison 

                    >Storage of calcium ions 

Rough ER :>Studded with numerous Ribosome 
                   >Process and transport protein synthesizes by ribosomes

GOLGI BODY

  >Consist of flattened memmranous sacs 
  >Function:Modifies processes or store the substance 

Cis Face:>Located near the ER to transport vesicle from ER to Golgi Body
               >Recive vesicle containing ER products from transport vesicles

Trans Face:>packages molecules in vesicles and transport them out of Golgi Body

LYSOSOME

>Spherical sacs 
>Surrounded by single membrane
>Contining hydrolytic enzyme 
>Function:Intercellular digestion such as Phagocytosis and Autophagy

Phagocytosis:>digesting food particle by engulfing

Autophagy:> digesting damage organelle

RIBOSOME

>Small granule 
>Consist of two subunit which is small and large 
>Non membranous
>Manufactured in nuclelous of nucleus
>Function:The site of protein synthesis.
                 Responsible for then formation of peptide bond

MITOCHONDRIA

>Double membrane
>Outer membrane:smooth 
 Inner membrane: convulated with enfolding called cristae
>Function:Site of cellular respiration

Cristae:>increase large surface are to make gaseous exchange more efficient

  CHLOROPLAST

>Double membrane
>Contain chlorophyll
>Contain its own DNA and Ribosome
>Function:Site of photosynthesis 
>Thylakoid:combination of grana(light reaction occurs)
>Stroma(dark reaction occurs)
>Integranal Lamella:connented thylakoid of adjacent grana

CENTROSOME AND CENTRIOLE

Centosome:region usually located near the nucleus

Centriole:A pair of short microtubules each composed of nine sets of triplets 
                 microtubules arranged in a ring 

>Function:Microtubule organizing centre and and important in cell division of animal cells.
                  Initiate the spindle that organizes and separates the chromosomes

VACOULE

>Single membrane 
>Membrane bound sacs containing water or dilute solution of salts and other solute
   called Cell Sap
>Function:> structural support
                  >storage for nutrient
                  >waste disposal
                  >protection
                  >growth

PASSIVE TRANSPORT

PASSIVE TRANSPORT

Naturally, molecules move from an area of high concentration to low concentration without the need of energy. This type of movement is passive transport. Molecules with strong electrical charges such as ions cannot simply diffuse across the cell membrane. Irrespective of their size, their charge prevents them from moving freely across the cell membrane. Other molecules such as proteins, starch and sugar are simply too large to diffuse across the membrane. Sometimes, some of these large molecules are transported across the cell membranes by carrier proteins; this does not require energy and as a result is a form of passive transport. There are three types of passive transport;

Simple diffusion: Hydrocarbons, carbon dioxide, and oxygen are hydrophobic substances that can pass easily across the cell membrane by diffusion and travel down the concentration gradient (Figure 8). This type of diffusion relies on the thermal motion energy intrinsic to the molecule in question. It is a form of passive transport because the cell expends no energy in moving the substances.

Figure 8: Diffusion of molecules across a semi-permeable membrane from an area of high concentration to an area of low concentration in order to achieve a balanced concentration.

Osmosis: The movement of water across a selectively permeable membrane is osmosis. A cell has one of three water relationships with the environment around it.

• In an isotonic solution there will be no net movement of water across the plasma membrane. Water crosses the membrane, but at the same rate in both directions.
• In a hypertonic solution the cell will lose water to its surroundings. The hyper - prefix refers to more solutes in the water around the cell, hence, the movement of water to the higher (hyper-) concentration of solutes. In this case the cell loses water to the environment, shrinks, and may die.
• In a hypotonic solution water will enter the cell faster than it leaves. The hypo - prefix refers to fewer solutes in the water around the cell, hence, the movement of water into the cell where the solutes are more heavily concentrated. In this case the cell will expand and may burst, unless protected by a cell wall such as that found in bacteria and plant cells.

Facilitated diffusion: Ions and polar molecules cannot pass easily across the membrane. The process by which ions and hydrophilic substances travel across the cell membrane with the help of transport proteins is called facilitated diffusion (Figure 9). Transport proteins are specific (like enzymes) for the substances they transport. They work in one of two ways:

• They provide a hydrophilic channel through which the molecules in question can pass.
• They bind loosely to the molecules in question and carry them through the membrane.

SODIUM-POTASSIUM PUMP CYCLE :) (SMILE)

SODIUM-POTASSIUM PUMP CYCLE

 

The sodium-potassium pump transports sodium out of and potassium into the cell in a repeating cycle of conformational (shape) changes. In each cycle, three sodium ions exit the cell, while two potassium ions enter. This process takes place in the following steps:

1. To begin, the pump is open to the inside of the cell. In this form, the pump really likes to bind (has a high affinity for) sodium ions, and will take up three of them.
2. When the sodium ions bind, they trigger the pump to hydrolyze (break down) ATP. One phosphate group from ATP is attached to the pump, which is then said to be phosphorylated. ADP is released as a by-product.
3. Phosphorylation makes the pump change shape, re-orienting itself so it opens towards the extracellular space. In this conformation, the pump no longer likes to bind to sodium ions (has a low affinity for them), so the three sodium ions are released outside the cell.
4. In its outward-facing form, the pump switches allegiances and now really likes to bind to (has a high affinity for) potassium ions. It will bind two of them, and this triggers removal of the phosphate group attached to the pump in step 2.
5. With the phosphate group gone, the pump will change back to its original form, opening towards the interior of the cell.
6. In its inward-facing shape, the pump loses its interest in (has a low affinity for) potassium ions, so the two potassium ions will be released into the cytoplasm. The pump is now back to where it was in step 1, and the cycle can begin again.

This may seem like a complicated cycle, but it just involves the protein going back and forth between two forms: an inward-facing form with high affinity for sodium (and low affinity for potassium) and an outward-facing form with high affinity for potassium (and low affinity for sodium). The protein can be toggled back and forth between these forms by the addition or removal of a phosphate group, which is in turn controlled by the binding of the ions to be transported.

CONNECTIVE TISSUE

CONNECTIVE TISSUE

HYALIN CARTILAGE:

STRUCTURE:

1.Firm and flexible                                                             

2.Chondrocytes(alive)

3.Cell of cartilage within lacunae

DISTRIBUTION:

1.Tachea 

2.Bronchi

FUNCTIONS

1.Covers the ends of bonds and reduces friction between joints during movement 

2.It  forms tge embryonic skeleton in many bony vertebrates

COMPACT BONE

STRUCTURE:

1.Living tissue 

2.Consist 

 (a)Osteocytes:Mature Osteoblasts

  

 ( b)Osteoblast:Form new bone and release calcium phosphate

  (c)Canaliculi:Contain cytoplasmic strands which connect the lacuna to each other

FUNCTIONS

1.Storage for calcium phosphorus

2.protect organ

3.Red blood cell production site

 

 

 

  

TIPS SMARTSTUDY(SS) FOR BIOLOGY

Building an UnderstandiNg

Learning is a process similar to building a house. You aren’t fed the complete picture. Limitations on communication prevent the instantaneous transmission of knowledge. Instead you listen to lectures, read textbooks and take painstaking notes to try and comprehend a subject.

You are fed building supplies, bricks, mortar and glass. It is up to you to assemble the building. Unfortunately, most learning strategies fall into two basic types:

1. Memorization – Instead of building anything you simply stare at each brick for several minutes trying to record its position.
2. Formulas – This is the equivalent to being blind, fumbling around a new house. You can’t see the building itself but you learn to come up with simple rules to avoid walking into walls.

There is nothing particularly wrong with either of these strategies, assuming they aren’t your entire strategy. The human brain isn’t a computer so it can’t memorize infinite sums of knowledge without some form of structure. And formulas no longer work if the questions they are designed to solve change scope.

Learning Holistically

The alternative strategy is to focus on actually using the information you have to build something. This involves linking concepts together and compressing information so it fits in the bigger picture. Here are some ideas to get started:

1. Metaphor – Metaphors can allow you to quickly organize information by comparing a complex idea to a simple one. When you find relationships between information, come up with analogies to increase your understanding. Compare neurons with waves on a string. Make metaphors comparing parts of a brain with sections of your computer.
2. Use All Your Senses – Abstract ideas are difficult to memorize because they are far removed from our senses. Shift them closer by coming up with vivid pictures, feelings and images that relate information together. When I learned how to do a determinant of a matrix, I remembered the pattern by visualizing my hands moving through the numbers, one adding and one subtracting.
3. Teach It – Find someone who doesn’t understand the topic and teach it to them. This exercise forces you to organize. Spending five minutes explaining a concept can save you an hour of combined studying for the same effect.
4. Leave No Islands – When you read through a textbook, every piece of information should connect with something else you have learned. Fast learners do this automatically, but if you leave islands of information, you won’t be able to reach them during a test.
5. Test Your Mobility – A good way to know you haven’t linked enough is that you can’t move between concepts. Open up a word document and start explaining the subject you are working with. If you can’t jump between sections, referencing one idea to help explain another, you won’t be able to think through the connections during a test.
6. Find Patterns – Look for patterns in information. Information becomes easier to organize if you can identify broader patterns that are similar across different topics. The way a neuron fires has similarities to “if” statements in programming languages.
7. Build a Large Foundation – Reading lots and having a general understanding of many topics gives you a lot more flexibility in finding patterns and metaphors in new topics. The more you already know, the easier it is to learn.
8. Don’t Force – I don’t spend much time studying before exams. Forcing information during the last few days is incredibly inefficient. Instead try to slowly interlink ideas as they come to you so studying becomes a quick recap rather than a first attempt at learning.
9. Build Models – Models are simple concepts that aren’t true by themselves, but are useful for describing abstract ideas. Crystallizing one particular mental image or experience can create a model you can reference when trying to understand. When I was trying to tackle the concept of subspaces, I visualized a blue background with a red plane going through it. This isn’t an entirely accurate representation of what a subspace is, but it created a workable image for future ideas.
10. Learning is in Your Head – Having beautiful notes and a perfectly highlighted textbook doesn’t matter if you don’t understand the information in it. Your only goal is to understand the information so it will stick with you for assignments, tests and life. Don’t be afraid to get messy when scrawling out ideas on paper and connecting them in your head. Use notes and books as a medium for learning rather than an end result.

PROTEIN

PROTEIN

Different proteins can appear very different and perform diverse functions (e.g. the water-soluble antibodies involved in the immune system and the water-insoluble keratin of hair, hooves and feathers). Despite this, each one is made up of amino acid subunits.

There about 20 different amino acids that all have a similar chemical structure but behave in very different ways because they have different side groups. Hence, stringing them together in different combinations produces very different proteins.

Each amino acid has an amino group (NH2) and a carboxylic acid group (COOH). The R group is a different molecule in different amino acids which can make them neutral, acidic, alkaline, aromatic (has a ring structure) or sulphur-containing.

When 2 amino acids are joined together (condensation) the amino group from one and the acid group from another form a bond, producing one molecule of water. The bond formed is called a peptide bond.

Hydrolysis is the opposite of condensation and is the breaking of a peptide bond using a molecule of water.

Primary structure of proteins

Due to the bonding and the shape and chemical nature of different amino acids, the shape of a whole chain of amino acids (a polypeptide or protein) is specific.

This will affect the properties of the protein, just as the type of a necklace depends on the type of beads and how they are strung together. Therefore, the primary structure depends on the order and number of amino acids in a particular protein.

For example:Haemoglobin is made up of 4 polypeptide chains, 2α chains and 2β chains, each with a haem group attached. There are 146 amino acids in each chain. If just one of these is wrong, serious problems can arise (e.g. sickle cell anaemia). The red blood cells become distorted, the amount of oxygen they can carry is reduced and blood capillaries can be blocked, leading to acute pains called crises.

Secondary structure of proteins

This is the basic shape that the chain of amino acids takes on. The 2 most common structures are the α-helix and the β-pleated sheet.

This has a regular coiled structure like a spring, with the R groups pointing towards the outside of the helix. Hydrogen (H) bonds are relatively weak but because there are so many, the total binding effect is strong and stable. The helix is flexible and elastic.

This is composed of 'side by side' chains connected by H bonds. All the peptide linkages are involved in inter-chain H bonding so the structure is very stable.

Tertiary structure of proteins

This is the overall 3-D structure of the protein.

The shape of the protein is held together by H bonds between some of the R groups (side chains) and ionic bonds between positively and negatively charged side chains. These are weak interactions, but together they help give the protein a stable shape. The protein may be reinforced by strong covalent bonds called disulphide bridges which form between two amino acids with sulphur groups on their side chains.

These interactions may be electrostatic attractions between charged groups e.g. NH3+ and O-or van der Waal's forces.

Fibrous proteins are made of long molecules arranged to form fibres (e.g. in keratin). Several helices may be wound around each other to form very strong fibres. Collagen is another fibrous protein, which has a greater tensile strength than steel because it consists of three polypeptide chains coiled round each other in a triple helix. We are largely held together by collagen as it is found in bones, cartilage, tendons and ligaments.

Globular proteins are made of chains folded into a compact structure. One of the most important classes are the enzymes. Although these folds are less regular than in a helix, they are highly specific and a particular protein will always be folded in the same way. If the structure is disrupted, the protein ceases to function properly and is said to be denatured. An example is insulin, a hormone produced by the pancreas and involved in blood sugar regulation.

A globular protein based mostly on an α-helix is haemoglobin.

A globular protein based mostly on a β-pleated sheet is the immunoglobulin antibody molecule.

Quaternary structure of proteins

If a protein is made up of several polypeptide chains, the way they are arranged is called thequaternary structure. Again, each protein formed has a precise and specific shape (e.g.haemoglobin)

Prosthetic groups

The majority of proteins are assisted in their functions by a prosthetic group. This may a simple metal ion such as zinc in the enzyme carboxypeptidase, or it may be a complex organic molecule, such as the haem group in haemoglobin.

Functions of proteins

1. Virtually all enzymes are proteins.
2. Structural: e.g. collagen and elastin in connective tissue, keratin in skin, hair and nails.
3. Contractile proteins: actin and myosin in muscles allow contraction and therefore movement.
4. Hormones: many hormones have a protein structure (e.g. insulin, glucagon, growth hormone).
5. Transport: for example, haemoglobin facilitates the transport of oxygen around the body, a type of albumin in the blood transports fatty acids.
6. Transport into and out of cells: carrier and channel proteins in the cell membrane regulate movement across it.
7. Defence: immunoglobulins (antibodies) protect the body against foreign invaders; fibrinogen in the blood is vital for the clotting process.

Biochemical test:

The reagent used to test for proteins is called biuret reagent. It can be used as two separate solutions of copper sulphate and potassium or sodium hydroxide or as a ready-made biuret solution. In either case, a purple colour indicates a positive result.

LIPIDS

LIPIDS

Lipids are made up of the elements carbon, hydrogen and oxygen but in different proportions to carbohydrates. The most common type of lipid is the triglyceride.

Lipids can exist as fats, oils and waxes. Fats and oils are very similar in structure (triglycerides).

At room temperature, fats are solids and oils are liquids. Fats are of animal origin, while oils tend to be found in plants.

Waxes have a different structure (esters of fatty acids with long chain alcohols) and can be found in both animals and plants.

TriglycerideS

These are made up of 3 fatty acid chains attached to a glycerol molecule.

Fatty acids are chains of carbon atoms, the terminal one having an OOH group attached making a carboxylic group (COOH). The length of the chain is usually between 14 and 22 carbons long (most commonly 16-18).

Three of these chains become attached to a glycerol molecule which has 3 OH groups attached to its 3 carbons. This is called a condensation reaction because 3 water molecules are formed from 3 OH groups from the fatty acids chains and 3 H atoms from the glycerol. The bond between the fatty acid chain and the glycerol is called an ester linkage.

The 3 fatty acids may be identical or they may have different structures.

In the fatty acid chains the carbon atoms may have single bonds between them making the lipid saturated. These are usually solid at room temperature and are called fats.

If one or more bonds between the carbon atoms are double bonds, the lipid is unsaturated. These are usually liquid at room temperature and are called oils.

Functions of lipids

1. Storage - lipids are non-polar and so are insoluble in water.
2. High-energy store - they have a high proportion of H atoms relative to O atoms and so yield more energy than the same mass of carbohydrate.
3. Production of metabolic water - some water is produced as a final result of respiration.
4. Thermal insulation - fat conducts heat very slowly so having a layer under the skin keeps metabolic heat in.
5. Electrical insulation - the myelin sheath around axons prevents ion leakage.
6. Waterproofing - waxy cuticles are useful, for example, to prevent excess evaporation from the surface of a leaf.
7. Hormone production - steroid hormones. Oestrogen requires lipids for its formation, as do other substances such as plant growth hormones.
8. Buoyancy - as lipids float on water, they can have a role in maintaining buoyancy in organisms.

Phospholipids

A phosphate-base group replaces one fatty acid chain. It makes this part of the molecule (the head) soluble in water whilst the fatty acid chains remain insoluble in water.

Due to this arrangement, phospholipids form bilayers (the main component of cell and organelle membranes).